This invention relates to a film and a support of the photographic material. This invention particularly relates to a film, which has a required level of strength, which does not easily suffer from roll set curl, which has good roll set curl eliminating properties, an appropriate level of curl in the width direction, and good handling properties, and which is useful as a film to be used as a printing material, a magnetic material, and a packaging material and to be used in the form of a roll. Also, this invention particularly relates to a support of the photographic material, which has good suitability for the processing apparatuses prior to a development process, good suitability for the processing apparatuses during the development process, and good handling properties after processes, and which is suitable for use in a silver halide light-sensitive photographic material.
At present, small-sized cameras, with which photographs can be taken easily and which is easy to handle and portable, have been put to practical use. However, from the point of view of portability and handiness, a need exists for smaller-sized cameras. In order for the sizes of cameras to be made smaller, it is essential to reduce the space, in which photographic film is accommodated.
Ordinarily, photographic film is wound up as a roll around a spool and is accommodated in this form in a camera. Therefore, such that the space required to accommodate the roll of film may be reduced and such that a roll of film having a predetermined number of frames (e.g. a 36-frame roll of film) may be accommodated in the reduced space, it is necessary to decrease the thickness of the photographic film. In particular, the thickness of a polyester film currently used as a support for photographic film is approximately 120 to 125 .mu.m and is thus markedly larger than the thickness (approximately 25 to 30 .mu.m) of a light-sensitive layer overlaid on the support. Therefore, it is considered that decreasing the thickness of the support is the most effective means for making the photographic film thin.
Typically, one end of a roll film having a width of 35 mm or smaller is connected to a spool, and the roll film is accommodated in this form in a patrone.
As specified in JIS K7519-1982, a roll film is provided with perforations at film side edges. In many cases, when the film is rewound in a camera, or the like, claws engage with the perforations of the film in order to rewind the film. If the strength of the perforated portions (i.e. the perforation strength) is low, the film will tear.
In general, the perforation strength is correlated to the breaking strength. If the breaking strength is higher, the perforation strength will become higher.
In general, the polyester film is obtained by carrying out melt extrusion to form an unoriented film, orienting the film in the longitudinal direction and then in the transverse direction, and thereafter subjecting the film to heat treatment. However, a copolymer polyethylene terephthalate (a copolymer PET) has markedly worse orientation properties than ordinary PET, and therefore cannot easily undergo sufficient molecular orientation. Therefore, the copolymer PET yields a film which has a low mechanical strength, particularly a low mechanical strength in the longitudinal direction. Also, the film, which has not been subjected to sufficient molecular orientation, has the drawbacks in that coating defects, such as streaks, grab failures, and coating nonuniformity, occur frequently during post-processes, i.e. the processes for coating functional layers, such as an adhesive layer, an anti-static layer, and a lubricant layer, and therefore the productivity cannot be kept high.
The reasons why the coating defects occur frequently have not yet been clarified. However, it is presumed that such coating defects occur frequently because, if the molecular orientation of the film is not sufficient, the flatness of the film will be lost due to heat treatment during the post-processes, and therefore stability during the coating cannot be obtained.
As conventional plastic film supports, triacetate films, such as films constituted of triacetyl cellulose (hereinafter often referred to as TAC), have typically been used. The TAC film originally has only a low mechanical strength and is therefore not suitable as a support of the photographic material which is to be made thinner than the thickness currently employed. Also, when the TAC film is produced, large amounts of methylene chloride are used. Therefore, various incidental facilities, such as recovery apparatuses, are required for the purposes of environmental protection, and the cost of the TAC film cannot be kept low.
Polyethylene terephthalate has also been used as a support of X-ray film and process film. By virtue of its high strength, the polyethylene terephthalate support may be applied to a color negative film. However, though the polyethylene terephthalate support has a high strength, it has the drawbacks in that it has bad roll set curl eliminating properties. Specifically, if the polyethylene terephthalate support undergoes roll set curl, it cannot get rid of the roll set curl after being subjected to a development process.
As a means for eliminating the roll set curl of a polyester support, methods for imparting the hydrophilic nature to the polyester support have been disclosed in, for example, Japanese Unexamined Patent Publication Nos. 2(1990)-120857 and 1(1989)-244446. However, the disclosed methods have the drawbacks in that, when a polyester support is merely rendered hydrophilic by the addition of amounts of copolymerization constituents, which amounts are required to improve the roll set curl eliminating properties of the support after being subjected to a development process to a level equivalent to the roll set curl eliminating properties of TAC, the level of roll set curl of the copolymer polyester support before being subjected to the development process rather becomes high, and therefore the good handling properties prior to the development process become bad. Particularly, in the current photographic field, a large number of sheets of film are spliced into a single film sheet by a splicer processing machine, and the spliced film sheet is developed in an automatic development processing machine for motion picture film. During the splicer processing, the leading end of the film provided with the hydrophilic copolymer polyester support, which has a very high level of roll set curl, cannot easily enter an inlet of the splicer processing machine. If the film is introduced forcibly into the splicer processing machine, the machine will be clogged with the film or the film will become folded.
Also, in cases where the PET film is used as a support of the photographic material, the support easily suffers from roll set curl during its storage at high temperatures due to large amounts of copolymerization constituents contained therein. In addition, blocking occurs between the front surface and the back surface of a light-sensitive material provided with the support, and scratches and spot-like defects are thereby caused to occur. Thus the PET film support has bad storage stability at high temperatures.
In Japanese Patent Application No. 2(1990)-208804, a light-sensitive photographic material is proposed which comprises laminated polyester layers having different water contents and which has good roll set curl eliminating properties and good mechanical properties, such as tear strength and folding endurance. However, with the proposed technique, the light-sensitive photographic material must contain large amounts of copolymerization constituents in order to obtain sufficient roll set curl eliminating properties. Therefore, the light-sensitive photographic material easily suffers from roll set curl and has bad storage stability at high temperatures, and the properties of the copolymer polyester layers themselves, such as the mechanical strength and dimensional stability, are lost. Accordingly, though the proposed technique has effects for improving the characteristics, such as the tear strength and folding endurance, upon which the properties of an inner polyester layer having a low water content are considered to reflect, the proposed technique has no effect for improving the mechanical strength and, in particular, the characteristics, such as the modulus of elasticity, which are related to the properties of the entire film.
As described above, the support of the photographic material is required to have storage stability at high temperatures. Also, at the stage at which a development process and drying have been finished, the support of the photographic material should exhibit little absorption of light having wavelengths falling within the short wavelength range (approximately 400 to 550 nm). A positive light-sensitive material, such as photographic paper, and a positive light-sensitive material for X-ray photographs have sensitivity to the short wavelength range. Therefore, if the support of the photographic material of a positive light-sensitive material absorbs light having wavelengths falling within the short wavelength range, the problems will occur in that the color formation of a yellow layer, which is primarily sensitive to the short wavelength range, is restricted during a printing process, and therefore a photograph is obtained in which the balance between the yellow color and the magenta and cyan colors is lost. If the support of the photographic material of a light-sensitive material for X-ray photographs absorbs light having wavelengths falling within the short wavelength range, the problems will occur in that filter desensitization effects occur when a photograph is taken, and an unsharp photograph containing defects like fog is obtained.
In order to solve the problems described above, the dependence of the spectral characteristics upon wavelengths may be relieved by adding a dye to the support of the photographic material. However, in such cases, the addition of a dye in an amount necessary to relieve the light absorption specificity for wavelengths falling within the short wavelength range causes the transmittance with respect to light having wavelengths falling within the middle wavelength range to decrease markedly. As a result, when the support of the photographic material is used for the positive light-sensitive material, such as photographic paper, the color balance cannot be improved very much, the entire color density becomes low, and there is the risk that an inappropriate photograph is ultimately obtained.
Also, in cases where the support of the photographic material is used for the positive light-sensitive material for X-ray film, a decrease in the transmittance of the base lead to a decrease in the image quality.
In order to solve the above-described problems, it is considered to increase the amounts of silver halides in the emulsion layer of the positive light-sensitive material or to alter the system setting, including the setting for photographing, for the positive light-sensitive material for X-ray photographs. However, as for the positive light-sensitive material, such as photographic paper, if the decrease in the film transmittance is compensated for by prolonging the exposure time during the printing process, the entire processing time cannot be kept short. Such a method is not appropriate because a need exists at present for a reduction in the entire processing time in view of a very large number of sheets of photographic paper to be processed.
In addition, silver halides are expensive, and therefore an increase in the amounts of silver halides leads to an increase in the cost of the light-sensitive material. Also, for the purposes of recovering silver, it is necessary for additional facilities to be provided. Further, silver halides entrained in the processing solutions during a development process, a fixing process, and the like, cause environmental pollution to occur. Moreover, alteration of the setting of processes in an automatic developing machine is practically impossible when the large scale of the current world-wide market is taken into consideration.
In view of the above-described problems, in the case where the support of the photographic material does not have good storage stability at high temperatures and specific spectral characteristics or a necessary color, it is not practically advantageous
A hydrophilic copolymer polyester support has a low strength due to copolymerization constituents contained therein. In cases where the film thickness is 100 .mu.m or less, the film becomes folded in an automatic development processing machine. Also, the film has no curl in the width direction, it is not easy to handle. Specifically, because the film is limp, there is a drawback that it readily buckles and causes film conveyance troubles to occur.
In order to obtain a thin film having good handling properties, particularly a light-sensitive photographic material which can be used in a small-sized camera, it is necessary to provide a thin support, which satisfies incompatible requirements such that it has a high strength and an appropriate level of curl in the width direction, such that it does not easily suffer from roll set curl and has good handling properties, and such that it has good roll set curl eliminating properties after being subjected to a water bath dipping treatment.
Also, if the flatness of the support of the photographic material is low, various coating defects occur in the post-processes. Therefore, the support of the photographic material should satisfy the requirement that its flatness is not adversely affected by heat treatment at high temperatures.